Epoxy dual cure resins for additive manufacturing

ABSTRACT

An epoxy dual cure resin useful for additive manufacturing of three-dimensional objects includes: (i) a photoinitiator; (ii) monomers and/or prepolymers that are polymerizable by exposure to actinic radiation or light; (iii) optionally, a light absorbing pigment or dye; (iv) an epoxy resin; (v) optionally, but in some embodiments preferably, an organic hardener co-polymerizable with the epoxy resin; (vi) optionally but preferably a dual reactive compound having substituted thereon a first reactive group reactive with said monomers and/or prepolymers that are polymerizable by exposure to actinic radiation or light, and a second reactive group reactive with said epoxy resin (e.g., an epoxy acrylate); (vii) optionally a diluent; (viii) optionally a filler; and (ix) optionally, a co-monomer and/or a co-prepolymer. Methods of using the same in additive manufacturing are also described.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/754,681, filed Feb. 23, 2018, which is a 35 U.S.C. § 371 nationalphase entry of International Application No. PCT/US2016/050043, filedSep. 2, 2016, and which claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/215,944 filed Sep. 9, 2015, 62/270,637 filedDec. 22, 2015, and 62/369,409 filed Aug. 1, 2016, the disclosures ofwhich are incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The present invention concerns materials, methods and apparatus for thefabrication of solid three-dimensional objects from liquid materials,and objects so produced.

BACKGROUND OF THE INVENTION

In conventional additive or three-dimensional fabrication techniques,construction of a three-dimensional object is performed in a step-wiseor layer-by-layer manner. In particular, layer formation is performedthrough solidification of photo curable resin under the action ofvisible or UV light irradiation. Two techniques are known: one in whichnew layers are formed at the top surface of the growing object; theother in which new layers are formed at the bottom surface of thegrowing object. An early example is Hull, U.S. Pat. No. 5,236,637. Otherapproaches are shown in U.S. Pat. Nos. 7,438,846, 7,892,474; M. Joyce,US Patent App. 2013/0292862; Y. Chen et al., US Patent App. 2013/0295212(both Nov. 7, 2013); Y. Pan et al., J. Manufacturing Sci. and Eng. 134,051011-1 (October 2012), and numerous other references. Materials foruse in such apparatus are generally limited, and there is a need for newresins which will provide diverse material properties for differentproduct families if three-dimensional fabrication is to achieve its fullpotential.

Southwell, Xu et al., US Patent Application Publication No.2012/0251841, describe liquid radiation curable resins for additivefabrication, but these comprise a cationic photoinitiator (and hence arelimited in the materials which may be used) and are suggested only forlayer by layer fabrication. See also U.S. Pat. No. 8,980,971 to Ueda(DSM).

Velankar, Pazos, and Cooper, Journal of Applied Polymer Science 162,1361 (1996), describe UV-curable urethane acrylates formed by adeblocking chemistry, but they are not suggested for additivemanufacturing, and no suggestion is made on how those materials may beadapted to additive manufacturing.

SUMMARY OF THE INVENTION

Accordingly, described herein is a method of forming a three-dimensionalobject is described herein. The method generally comprises:

(a) providing an epoxy dual cure resin (sometimes also referred toherein as a “polymerizable liquid”);

(b) forming a three-dimensional intermediate from said resin, where saidintermediate has the shape of, or a shape to be imparted to, saidthree-dimensional object, and where said resin is solidified by exposureto light; then

(c) optionally, but in some embodiments preferably, washing the threedimensional intermediate, and then

(d) heating and/or microwave irradiating said three-dimensionalintermediate sufficiently to further cure said resin and form saidthree-dimensional object;

wherein said epoxy dual cure resin comprises:

-   -   (i) a photoinitiator;    -   (ii) monomers and/or prepolymers that are polymerizable by        exposure to actinic radiation or light;    -   (iii) optionally, a light absorbing pigment or dye;    -   (iv) an epoxy resin;    -   (v) optionally, but in some embodiments preferably, an organic        hardener co-polymerizable with said epoxy resin;    -   (vi) optionally, but preferably, a dual reactive compound having        substituted thereon a first reactive group reactive with said        monomers and/or prepolymers that are polymerizable by exposure        to actinic radiation or light, and a second reactive group        reactive with said epoxy resin;    -   (vii) optionally a diluent;    -   (viii) optionally a filler (e.g., silica, a toughener such as a        core-shell rubber, etc., including combinations thereof); and    -   (ix) optionally, a co-monomer and/or a co-prepolymer.

Resins useful for carrying out such methods, and products produced fromsuch methods, are also described.

In some embodiments, a Lewis acid or an oxidizable tin salt is includedin the polymerizable liquid or resin (e.g., in an amount of from 0.01 or0.1 to 1 or 2 percent by weight, or more) in an amount effective toaccelerate the formation of the three-dimensional intermediate objectduring the production thereof.

In some embodiments of the methods and compositions described above andbelow, the polymerizable liquid (or “dual cure resin”) has a viscosityof 100, 200, 500 or 1,000 centipoise or more at room temperature and/orunder the operating conditions of the method, up to a viscosity of10,000, 20,000, or 50,000 centipoise or more, at room temperature and/orunder the operating conditions of the method.

The resins and methods described herein are particularly useful forforming three-dimensional objects that are rigid, exhibit high tensilestrength, exhibit high scratch resistance, exhibit a high glasstransition temperature, provide good chemical resistance, and/or aregood insulators (e.g., for electrical applications).

In some embodiments, polymerizable liquids used in the present inventioninclude a non-reactive pigment or dye. Examples include, but are notlimited to, (i) titanium dioxide (e.g., in an amount of from 0.05 or 0.1to 1 or 5 percent by weight), (ii) carbon black (e.g., included in anamount of from 0.05 or 0.1 to 1 or 5 percent by weight), and/or (iii) anorganic ultraviolet light absorber such as a hydroxybenzophenone,hydroxyphenylbenzotriazole, oxanilide, benzophenone, thioxanthone,hydroxyphenyltriazine, and/or benzotriazole ultraviolet light absorber(e.g. in an amount of 0.001 or 0.005 to 1, 2 or 4 percent by weight).

Non-limiting examples and specific embodiments of the present inventionare explained in greater detail in the specification set forth below.The disclosures of all United States Patent references cited herein areto be incorporated herein by reference in their entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: Results with an aromatic amine hardener system without CN153(top), and with CN153 (bottom).

FIG. 2: Results with an anhydride hardener system without CN153 (top),and with CN153 (bottom).

FIG. 3: Results with a polyether amine hardener system without CN153(left), and with CN153 (right).

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention is now described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein; rather these embodiments are provided sothat this disclosure will be thorough and complete and will fully conveythe scope of the invention to those skilled in the art.

As used herein, the term “and/or” includes any and all possiblecombinations or one or more of the associated listed items, as well asthe lack of combinations when interpreted in the alternative (“or”).

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the specification andclaims and should not be interpreted in an idealized or overly formalsense unless expressly so defined herein. Well-known functions orconstructions may not be described in detail for brevity and/or clarity.

“Shape to be imparted to” refers to the case where the shape of theintermediate object slightly changes between formation thereof andforming the subsequent three-dimensional product, typically by shrinkage(e.g., up to 1, 2 or 4 percent by volume), expansion (e.g., up to 1, 2or 4 percent by volume), removal of support structures, or byintervening forming steps (e.g., intentional bending, stretching,drilling, grinding, cutting, polishing, or other intentional formingafter formation of the intermediate product, but before formation of thesubsequent three-dimensional product).

1. Resins.

As noted above, the present invention includes epoxy dual cure resincompositions useful for additive manufacturing. Such compositionscomprise, consist of, or consist essentially of:

-   -   (i) a photoinitiator;    -   (ii) monomers and/or prepolymers that are polymerizable by        exposure to actinic radiation or light;    -   (iii) optionally, a light absorbing pigment or dye;    -   (iv) an epoxy resin;    -   (v) optionally, but in some embodiments preferably, an organic        hardener co-polymerizable with said epoxy resin;    -   (vi) optionally but preferably a dual reactive compound having        substituted thereon a first reactive group reactive with said        monomers and/or prepolymers that are polymerizable by exposure        to actinic radiation or light, and a second reactive group        reactive with said epoxy resin;    -   (vii) optionally a diluent;    -   (viii) optionally a filler; and    -   (ix) optionally, a co-monomer and/or a co-prepolymer.

In some embodiments, the epoxy resin comprises a bisphenol A epoxyresin, a bisphenol F epoxy resin, a novolac epoxy resin, an aliphaticepoxy resin, a glycidylamine epoxy resin, or a combination thereof. Insome embodiments, the epoxy resin comprises an epoxy compound having atleast two epoxy groups; in other embodiments epoxy resin can compriseand epoxy compound having a single epoxy group, for example as areactive diluent. Numerous examples of suitable epoxy resins (andorganic hardeners) are known. See, e.g., U.S. Pat. Nos. 3,945,972;3,947,395, 4,833,226; 5,319,004; 6,355,763; 6,881,813; 8,383,025;9,133,301; etc.

In some embodiments, the epoxy resin comprises an epoxidized vegetableoil. In general, epoxidized vegetable oils can be obtained by theepoxidation of triglycerides of unsaturated fatly acids. They are madeby epoxidizing the reactive olefin groups of the naturally occurringtriglyceride oils. The olefin groups can be epoxidized with peracids,such as perbenzoic, peracetic and the like, and with hydrogen peroxide.Suitable epoxidized vegetable oils are epoxidized linseed oil,epoxidized soybean oil, epoxidized corn oil, epoxidized cottonseed oil,epoxidized perilla oil, epoxidized safflower oil, etc. See, e.g., U.S.Pat. Nos. 3,051,671; 5,973,082; 8,481,622; and 9,169,386; see also M.Stemmelen et al., A fully biobased epoxy resin from vegetable oils: Fromthe synthesis of the precursors by thiol-ene reaction to the study ofthe final material, J. Polym Sci. Part A: Polym Chem. 49, 2434-2444(2011).

In some embodiments, the epoxy resin comprises a catalyzed epoxy resin(which may not require a hardener). In such case, the resin may furtherinclude an epoxy homopolymerization catalyst, such as a tertiary amineor imidizole (anionic polymerization) or boron trifluoride (cationicpolymerizations).

Any suitable hardener may be used (see references cited in connectionwith epoxy resins above). In some embodiments, the hardener comprises anamine or polyamine (e.g., an aromatic amine or polyamine, acycloaliphatic amine or polyamine, an aliphatic amine or polyamine suchas a polyether amine, etc.).

In some embodiments, the hardener comprises an acid or polyacid (i.e.,polycarboxylic acids), a phenol or polyphenol, an alcohol or polyol, ora thiol or polythiol.

In some embodiments, the hardener comprises an anhydride, such as alinear or cyclic anhydride, including compounds having more than oneanhydride group (for example, at least one of polysebacic or polyazelaicanhydride; methyltetrahydrophthalic anhydride, tetrahydro phthalicanhydride, methyl nadic anhydride, hexahydro phthalicanhydride, andmethylhexahydro phthalic anhydride; succinic anhydride, substitutedsuccinic anhydride, citric acid anhydride, maleic anhydride, adducts ofmaleic anhydride, dodecyl succinic anhydride, maleic anhydride vinyl andstyrene copolymers of maleic anhydride, multi-ring alicyclic anhydrides,phthalic anhydride, and/or trimellitic anhydride (See, e.g., U.S. Pat.No. 9,080,007)).

Latent hardeners. In some embodiments, the hardener comprises a latenthardener (including mixtures thereof): That is, a hardener having a lowreactivity at lower temperatures, and/or which is sparingly soluble atlower temperatures, such that the hardener can be more stable at roomtemperature, but then activated upon heating. Numerous examples oflatent hardeners are known (See, e.g., U.S. Pat. No. 8,779,036; see alsoU.S. Pat. No. 4,859,761. Particular examples include substitutedguanidines and aromatic amines, such as dicyandiamide, benzoguanamine,o-tolylbiguanidine, bis(4-aminophenyl) sulfone (also known as diaminodiphenylsulfone: DDS), bis(3-aminophenyl) sulfone,4,4′-methylenediamine, 1,2- or 1,3- or 1,4-benzenediamines,bis(4-aminophenyl)-1,4-diisopropylbenzene (e.g. EPON 1061 from Shell),bis(4-amino-3,5-dimethylphenyl)-1,4-diisopropylbenzene (e.g. EPON 1062from Shell), bis(aminophenyl) ether, diaminobenzophenones,2,6-diaminopyridine, 2,4-toluenediamine, diaminodiphenylpropanes,1,5-diaminonaphthalene, xylenediamines,1,1-bis-4-aminophenylcyclohexane, methylenebis(2,6-diethylaniline) (e.g.LONZACURE M-DEA from Lonza), methylenebis(2-isopropyl-6-methylaniline)(e.g. LONZACURE M-MIPA from Lonza), methylenebis(2,6-diisopropylaniline)(e.g. LONZACURE M-DIPA from Lonza), 4-aminodiphenylamine,diethyltoluenediamine, phenyl-4,6-diaminotriazine, andlauryl-4,6-diaminotriazine. Still other examples includeN-acylimidazoles such as 1-(2′,4′,6′-trimethylbenzoyl)-2-phenylimidazoleor 1-benzoyl-2-isopropylimidazole (see, e.g., U.S. Pat. Nos. 4,436,892and 4,587,311); Cyanoacetyl compounds such as neopentyl glycolbiscyanoacetate, N-isobutylcyanoacetamide, 1,6-hexamethylenebiscyanoacetate or 1,4-cyclohexanedimethanol biscyanoacetate (see, e.g.,U.S. Pat. No. 4,283,520); N-cyanoacylamide compounds such asN,N′-dicyanoadipic diamide (see, e.g., U.S. Pat. Nos. 4,529,821,4,550,203, and 4,618,712; acylthiopropylphenols (see, e.g., U.S. Pat.No. 4,694,096) and the urea derivatives such astoluene-2,4-bis(N,N-dimethylcarbamide) (see, e.g., U.S. Pat. No.3,386,955); and aliphatic or cycloaliphatic diamines and polyamines ifthey are sufficiently unreactive. An example which may be mentioned hereis polyetheramines, e.g. JEFFAMINE 230 and 400. Aliphatic orcycloaliphatic diamines or polyamines whose reactivity has been reducedby steric and/or electronic influencing factors or/and are sparinglysoluble or have a high melting point, e.g. JEFFLINK 754 (Huntsman) orCLEARLINK 1000 (Dorf Ketal) can also be used.

Epoxy accelerator. An accelerator (or mixture of accelerators) mayoptionally be included in the polymerizable liquid, examples of whichinclude but are not limited to those set forth in U.S. Pat. Nos.9,080,007; 8,779,036; 7,750,107; 6,773,754; 5,198,146; 4,800,222; and3,639,928.

In some embodiments, the monomers and/or prepolymers polymerizable byexposure to actinic radiation or light are those comprising reactive endgroups selected from the group consisting of acrylates, methacrylates,α-olefins, N-vinyls, acrylamides, methacrylamides, styrenics, epoxides,thiols, 1,3-dienes, vinyl halides, acrylonitriles, vinyl esters,maleimides, and vinyl ethers. (See, e.g., US Patent ApplicationPublication No. 2015/0072293 to DeSimone et al. see also: Rolland etal., Three dimensional objects produced from materials having multiplemechanisms of hardening, US Patent Application Pub. No. 2016016077 (9Jun. 2016) (also published as PCT Patent Application Pub. No.WO2015/200189); Rolland et al., Methods of producing three dimensionalobjects from materials having multiple mechanisms of hardening US PatentApplication Pub. No. 20160136889 (19 May 2016) (also published as PCTPatent Application Pub. No. WO2015/200173); Rolland et al., Methods ofproducing polyurethane three-dimensional objects from materials havingmultiple mechanisms of hardening US Patent Application Pub. No.20160137838 (19 May 2016) (also published as PCT Patent Application Pub.No. WO2015/200179); and Rolland et al., Polyurethane resins havingmultiple mechanisms of hardening for use in producing three-dimensionalobjects US Patent Application Pub. No. 20160137839 (19 May 2016) (alsopublished as PCT Patent Application Pub. No. WO2015/200201), thedisclosures of all of which are incorporated by reference herein intheir entirety. In some embodiments, acrylated or methacrylatedvegetable oils may be employed; in some embodiments, acrylated ormethacrylated polyols (e.g., sucrose polyesters such as SEFOSE™ brandsucrose polyester) may be used as the monomers and/or prepolymerspolymerizable by exposure to actinic radiation or light. See, e.g., U.S.Pat. No. 8,574,558.

Dual reactive compound. As noted above, in some embodiments a dualreactive compound is included in the polymerizable liquid. In general,such a dual reactive compound comprises: (i) a first reactive groupreactive with (i.e., preferentially reactive with) the monomers and/orprepolymers that are polymerizable by exposure to actinic radiation orlight, and (ii) a second reactive group reactive with (i.e.,preferentially reactive with) the epoxy resin. One or more of eachreactive groups may be included.

Examples of suitable first reactive groups include, but are not limitedto, acrylates, methacrylates, α-olefins, N-vinyls, acrylamides,methacrylamides, styrenics, thiols, 1,3-dienes, vinyl halides,acrylonitriles, vinyl esters, maleimides, and vinyl ethers.

Examples of suitable second reactive groups include, but are not limitedto, epoxy, amine, isocyanate, alcohol, and anhydride groups.

Thus, particular examples of suitable dual reactive compounds includecompounds of the general formula (X)_(n)R(V)_(m), wherein: X is thefirst reactive group, X′ is the second reactive group, n and m are eachintegers of from 1 or 2 to 10 or 20, and R is a hydrocarbyl or organicgroup (e.g., an aromatic, aliphatic, or mixed aromatic and aliphaticgroup, such as bis-phenol a). Particular examples include but are notlimited to epoxy acrylates and epoxy methacrylates, such as compounds ofFormula I:

where R′ is H or CH₃ and R is as given above. R may be as short as —CH₂—(e.g., glicidyl methacrylate), or may be a long chain organic polymeritself. See, e.g., U.S. Pat. No. 8,383,025 at column 4.

Lewis acids and oxidizable tin salts. In some embodiments, a Lewis acidor an oxidizable tin salt is included in the polymerizable liquid (e.g.,in an amount of from 0.01 or 0.1 to 1 or 2 percent by weight, or more)in an amount effective to accelerate the formation of thethree-dimensional intermediate object during the production thereof.Oxidizable tin salts useful for carrying out the present inventioninclude, but are not limited to, stannous butanoate, stannous octoate,stannous hexanoate, stannous heptanoate, stannous linoleate, stannousphenyl butanoate, stannous phenyl stearate, stannous phenyl oleate,stannous nonanoate, stannous decanoate, stannous undecanoate, stannousdodecanoate, stannous stearate, stannous oleate stannous undecenoate,stannous 2-ethylhexoate, dibutyl tin dilaurate, dibutyl tin dioleate,dibutyl tin distearate, dipropyl tin dilaurate, dipropyl tin dioleate,dipropyl tin distearate, dibutyl tin dihexanoate, and combinationsthereof. See also U.S. Pat. Nos. 5,298,532; 4,421,822; and 4,389,514,the disclosures of which are incorporated herein by reference. Inaddition to the foregoing oxidizable tin salts, Lewis acids such asthose described in Chu et al. in Macromolecular Symposia, Volume 95,Issue 1, pages 233-242, June 1995 are known to enhance thepolymerization rates of free-radical polymerizations and are includedherein by reference.

Fillers. Any suitable filler may be used in connection with the presentinvention, depending on the properties desired in the part or object tobe made. Thus, fillers may be solid or liquid, organic or inorganic, andmay include reactive and non-reactive rubbers: siloxanes,acrylonitrile-butadiene rubbers; reactive and non-reactivethermoplastics (including but not limited to: poly(ether imides),maleimide-styrene terpolymers, polyarylates, polysulfones andpolyethersulfones, etc.) inorganic fillers such as silicates (such astalc, clays, silica, mica), glass, carbon nanotubes, graphene, cellulosenanocrystals, etc., including combinations of all of the foregoing.Suitable fillers include tougheners, such as core-shell rubbers, asdiscussed below.

Tougheners. One or more polymeric and/or inorganic tougheners can beused as a filler in the present invention. See generally US PatentApplication Publication No. 20150215430. The toughener may be uniformlydistributed in the form of particles in the cured product. The particlescould be less than 5 microns (um) in diameter. Such tougheners include,but are not limited to, those formed from elastomers, branched polymers,hyperbranched polymers, dendrimers, rubbery polymers, rubberycopolymers, block copolymers, core-shell particles, oxides or inorganicmaterials such as clay, polyhedral oligomeric silsesquioxanes (POSS),carbonaceous materials (e.g., carbon black, carbon nanotubes, carbonnanofibers, fullerenes), ceramics and silicon carbides, with or withoutsurface modification or functionalization. Examples of block copolymersinclude the copolymers whose composition is described in U.S. Pat. No.6,894,113 (Court et al., Atofina, 2005) and include “NANOSTRENTH®™” SBM(polystyrene-polybutadiene-polymethacrylate), and AMA(polymethacrylate-polybutylacrylate-polymethacrylate), both produced byArkema. Other suitable block copolymers include FORTEGRA®™ and theamphiphilic block copolymers described in U.S. Pat. No. 7,820,760B2,assigned to Dow Chemical. Examples of known core-shell particles includethe core-shell (dendrimer) particles whose compositions are described inUS20100280151A1 (Nguyen et al., Toray Industries, Inc., 2010) for anamine branched polymer as a shell grafted to a core polymer polymerizedfrom polymerizable monomers containing unsaturated carbon-carbon bonds,core-shell rubber particles whose compositions are described in EP1632533A1 and EP 2123711A1 by Kaneka Corporation, and the “KaneAce MX”product line of such particle/epoxy blends whose particles have apolymeric core polymerized from polymerizable monomers such asbutadiene, styrene, other unsaturated carbon-carbon bond monomer, ortheir combinations, and a polymeric shell compatible with the epoxy,typically polymethylmethacrylate, polyglycidylmethacrylate,polyacrylonitrile or similar polymers, as discussed further below. Alsosuitable as block copolymers in the present invention are the “JSR SX”series of carboxylated polystyrene/polydivinylbenzenes produced by JSRCorporation; “Kureha Paraloid” EXL-2655 (produced by Kureha ChemicalIndustry Co., Ltd.), which is a butadiene alkyl methacrylate styrenecopolymer; “Stafiloid” AC-3355 and TR-2122 (both produced by TakedaChemical Industries, Ltd.), each of which are acrylate methacrylatecopolymers; and “PARALOID” EXL-2611 and EXL-3387 (both produced by Rohm& Haas), each of which are butyl acrylate methyl methacrylatecopolymers. Examples of suitable oxide particles include NANOPDX®™produced by nanoresins AG. This is a master blend of functionalizednanosilica particles and an epoxy.

Core-shell rubbers. Core-shell rubbers are particulate materials(particles) having a rubbery core. Such materials are known anddescribed in, for example, US Patent Application Publication No.20150184039, as well as US Patent Application Publication No.20150240113, and U.S. Pat. Nos. 6,861,475, 7,625,977, 7,642,316,8,088,245, and elsewhere.

In some embodiments, the core-shell rubber particles are nanoparticles(i.e., having an average particle size of less than 1000 nanometers(nm)). Generally, the average particle size of the core-shell rubbernanoparticles is less than 500 nm, e.g., less than 300 nm, less than 200nm, less than 100 nm, or even less than 50 nm. Typically, such particlesare spherical, so the particle size is the diameter; however, if theparticles are not spherical, the particle size is defined as the longestdimension of the particle.

In some embodiments, the rubbery core can have a Tg of less than −25°C., more preferably less than −50° C., and even more preferably lessthan −70° C. The Tg of the rubbery core may be well below −100° C. Thecore-shell rubber also has at least one shell portion that preferablyhas a Tg of at least 50° C. By “core,” it is meant an internal portionof the core-shell rubber. The core may form the center of the core-shellparticle, or an internal shell or domain of the core-shell rubber. Ashell is a portion of the core-shell rubber that is exterior to therubbery core. The shell portion (or portions) typically forms theoutermost portion of the core-shell rubber particle. The shell materialcan be grafted onto the core or is cross-linked. The rubbery core mayconstitute from 50 to 95%, or from 60 to 90%, of the weight of thecore-shell rubber particle.

The core of the core-shell rubber may be a polymer or copolymer of aconjugated diene such as butadiene, or a lower alkyl acrylate such asn-butyl-, ethyl-, isobutyl- or 2-ethylhexylacrylate. The core polymermay in addition contain up to 20% by weight of other copolymerizedmono-unsaturated monomers such as styrene, vinyl acetate, vinylchloride, methyl methacrylate, and the like. The core polymer isoptionally cross-linked. The core polymer optionally contains up to 5%of a copolymerized graft-linking monomer having two or more sites ofunsaturation of unequal reactivity, such as diallyl maleate, monoallylfumarate, allyl methacrylate, and the like, at least one of the reactivesites being non-conjugated.

The core polymer may also be a silicone rubber. These materials oftenhave glass transition temperatures below −100° C. Core-shell rubbershaving a silicone rubber core include those commercially available fromWacker Chemie, Munich, Germany, under the trade name Genioperl.

The shell polymer, which is optionally chemically grafted orcross-linked to the rubber core, can be polymerized from at least onelower alkyl methacrylate such as methyl methacrylate, ethyl methacrylateor t-butyl methacrylate. Homopolymers of such methacrylate monomers canbe used. Further, up to 40% by weight of the shell polymer can be formedfrom other monovinylidene monomers such as styrene, vinyl acetate, vinylchloride, methyl acrylate, ethyl acrylate, butyl acrylate, and the like.The molecular weight of the grafted shell polymer can be between 20,000and 500,000.

One suitable type of core-shell rubber has reactive groups in the shellpolymer which can react with an epoxy resin or an epoxy resin hardener.Glycidyl groups are suitable. These can be provided by monomers such asglycidyl methacrylate.

One example of a suitable core-shell rubber is of the type described inUS Patent Application Publication No. 2007/0027233 (EP 1 632 533 A1).Core-shell rubber particles as described therein include a cross-linkedrubber core, in most cases being a cross-linked copolymer of butadiene,and a shell which is preferably a copolymer of styrene, methylmethacrylate, glycidyl methacrylate and optionally acrylonitrile. Thecore-shell rubber is preferably dispersed in a polymer or an epoxyresin, also as described in the document.

Suitable core-shell rubbers include, but are not limited to, those soldby Kaneka Corporation under the designation Kaneka Kane Ace, includingthe Kaneka Kane Ace 15 and 120 series of products, including KanakaKance Ace MX 120, Kaneka Kane Ace MX 153, Kaneka Kane Ace MX 154, KanekaKane Ace MX 156, Kaneka Kane Ace MX170, and Kaneka Kane Ace MX 257 andKaneka Kane Ace MX 120 core-shell rubber dispersions, and mixturesthereof.

In some embodiments, the light absorbing pigment or dye is:

(i) titanium dioxide (e.g., in an amount of from 0.05 or 0.1 to 1 or 5percent by weight),

(ii) carbon black (e.g., in an amount of from 0.05 or 0.1 to 1 or 5percent by weight), and/or

(iii) an organic ultraviolet light absorber (e.g., ahydroxybenzophenone, hydroxyphenylbenzotriazole, oxanilide,benzophenone, thioxanthone, hydroxyphenyltriazine, and/or benzotriazoleultraviolet light absorber) (e.g., in an amount of 0.001 or 0.005 to 1or 2 percent by weight).

In some embodiments, the diluent comprises an acrylate, a methacrylate,a styrene, an acrylic acid, a vinylamide, a vinyl ether, a vinyl ester,polymers containing any one or more of the foregoing, and combinationsof two or more of the foregoing.

Microwave absorbing materials. In some embodiments, the polymerizableliquid contains a microwave absorbing, or microwave dissipative,materials. Such materials are generally particles, and in some casesnanoparticles. Such materials are known. See, e.g., U.S. Pat. No.5,189,078; see also U.S. Pat. Nos. 6,566,414, 7,273,580, 4,626,642; andPCT Patent Application WO 2013/021039. Particular examples of suitablematerials include, but are not limited to, iron, tungsten, chromium,aluminum, copper, titanium, titanium nitride, molybdenum disilicide,nickel, and carbon (including graphite). Suitable spherical substratesinclude ceramics (including glass), metals and polymers. In someembodiments, the particles may range in diameter from 0.1 to 150microns. One type of particles is acicular magnetic metallicpolycrystalline filaments which have an average length of about 10microns or less, diameters of about 0.1 micron or more, and aspectratios between 50:1 and 10:1, Other suitable particles are based on ironoxide filaments: ferric oxide itself; ferrosoferric oxide having a thinsurface layer of adsorbed cobalt, with x between 1.0 and 1.5 and thesurface cobalt providing one to ten percent of the particle weight, inacicular form of length 0.4 micron and aspect ratio about 6:1 to 8:1; orsimilarly shaped and sized ferric oxide filaments having a thin surfacelayer of adsorbed cobalt and doubly ionized iron atoms. In someembodiments, the microwave absorbing material may comprise ironnanoparticles. See, e.g., X. F. Sun et al., Study on the Properties ofMicrowave Curing Epoxy Resin/Nano-Fe Composite Materials, AppliedMechanics and Materials 26-28, pp. 356-359 (2010). In some embodiments,the microwave absorbing material may comprise an inorganic pigmentand/or filler. See, e.g., D. Kersting and H. Wiebeck, Evaluation of theuse of inorganic pigments and fillers in cure of epoxy resins bymicrowave irradiation, 2013 International Nuclear AtlanticConference—INAC 2013.

When present, microwave absorbing materials such as described above maybe included in the resin composition, for both the photopolymerizationstep and the microwave/heat polymerization step, in any suitable amount,typically from 0.1 or 1 to 5, 10 or 20 percent by weight, or more.

In some embodiments, the polymerizable liquid comprises:

(i) from 0.1 to 4 percent by weight of said photoinitiator,

(ii) from 10 to 90 percent by weight of said monomers and/or prepolymersthat are polymerizable by exposure to actinic radiation or light,

(iii) from 0.1 to 2 percent by weight of said light absorbing pigment ordye when present,

(iv) from 2, 5 or 10 to 50 or 60 percent by weight of said epoxy resin;

(v) from 1 or 2 to 30 or 40 percent by weight of said organic hardenerwhen present; (vi) from 1 or 2 to 30 or 40 percent by weight of saiddual reactive compound, when present;

(vii) from 1 or 2 to 30 or 40 percent by weight of said diluent whenpresent; and

(viii) from 1 or 2 to 20, 30 or 50 percent by weight of said filler whenpresent.

2. Methods.

The three dimensional intermediate is preferably formed from resins asdescribed above by additive manufacturing, typically bottom-up ortop-down additive manufacturing. Such methods are known and describedin, for example, U.S. Pat. No. 5,236,637 to Hull, U.S. Pat. Nos.5,391,072 and 5,529,473 to Lawton, U.S. Pat. No. 7,438,846 to John, U.S.Pat. No. 7,892,474 to Shkolnik, U.S. Pat. No. 8,110,135 to El-Siblani,U.S. Patent Application Publication Nos. 2013/0292862 to Joyce and2013/0295212 to Chen et al., and PCT Application Publication No. WO2015/164234 to Robeson et al. The disclosures of these patents andapplications are incorporated by reference herein in their entirety.

In general, top-down three-dimensional fabrication is carried out by:

(a) providing a polymerizable liquid reservoir having a polymerizableliquid fill level and a carrier positioned in the reservoir, the carrierand the fill level defining a build region therebetween;

(b) filling the build region with a polymerizable liquid (i.e., theresin), said polymerizable liquid comprising a mixture of (i) a light(typically ultraviolet light) polymerizable liquid first component, and(ii) a second solidifiable component of the dual cure system; and then

(c) irradiating the build region with light to form a solid polymerscaffold from the first component and also advancing (typicallylowering) the carrier away from the build surface to form athree-dimensional intermediate having the same shape as, or a shape tobe imparted to, the three-dimensional object and containing said secondsolidifiable component (e.g., a second reactive component) carried inthe scaffold in unsolidified and/or uncured form.

A wiper blade, doctor blade, or optically transparent (rigid orflexible) window, may optionally be provided at the fill level tofacilitate leveling of the polymerizable liquid, in accordance withknown techniques. In the case of an optically transparent window, thewindow provides a build surface against which the three dimensionalintermediate is formed, analogous to the build surface in bottom-upthree dimensional fabrication as discussed below.

In general, bottom-up three dimensional fabrication is carried out by:

(a) providing a carrier and an optically transparent member having abuild surface, the carrier and the build surface defining a build regiontherebetween;

(b) filling the build region with a polymerizable liquid (i.e., theresin), said polymerizable liquid comprising a mixture of (i) a light(typically ultraviolet light) polymerizable liquid first component, and(ii) a second solidifiable component of the dual cure system; and then

(c) irradiating the build region with light through said opticallytransparent member to form a solid polymer scaffold from the firstcomponent and also advancing (typically raising) the carrier away fromthe build surface to form a three-dimensional intermediate having thesame shape as, or a shape to be imparted to, the three-dimensionalobject and containing said second solidifiable component (e.g., a secondreactive component) carried in the scaffold in unsolidified and/oruncured form.

In some embodiments of bottom up or top down three dimensionalfabrication as implemented in the context of the present invention, thebuild surface is stationary during the formation of the threedimensional intermediate; in other embodiments of bottom-up threedimensional fabrication as implemented in the context of the presentinvention, the build surface is tilted, slid, flexed and/or peeled,and/or otherwise translocated or released from the growing threedimensional intermediate, usually repeatedly, during formation of thethree dimensional intermediate.

In some embodiments of bottom up or top down three dimensionalfabrication as carried out in the context of the present invention, thepolymerizable liquid (or resin) is maintained in liquid contact withboth the growing three dimensional intermediate and the build surfaceduring both the filling and irradiating steps, during fabrication ofsome of, a major portion of, or all of the three dimensionalintermediate.

In some embodiments of bottom-up or top down three dimensionalfabrication as carried out in the context of the present invention, thegrowing three dimensional intermediate is fabricated in a layerlessmanner (e.g., through multiple exposures or “slices” of patternedactinic radiation or light) during at least a portion of the formationof the three dimensional intermediate.

In some embodiments of bottom up or top down three dimensionalfabrication as carried out in the context of the present invention, thegrowing three dimensional intermediate is fabricated in a layer-by-layermanner (e.g., through multiple exposures or “slices” of patternedactinic radiation or light), during at least a portion of the formationof the three dimensional intermediate.

In some embodiments of bottom up or top down three dimensionalfabrication employing a rigid or flexible optically transparent window,a lubricant or immiscible liquid may be provided between the window andthe polymerizable liquid (e.g., a fluorinated fluid or oil such as aperfluoropolyether oil).

From the foregoing it will be appreciated that, in some embodiments ofbottom-up or top down three dimensional fabrication as carried out inthe context of the present invention, the growing three dimensionalintermediate is fabricated in a layerless manner during the formation ofat least one portion thereof, and that same growing three dimensionalintermediate is fabricated in a layer-by-layer manner during theformation of at least one other portion thereof. Thus, operating modemay be changed once, or on multiple occasions, between layerlessfabrication and layer-by-layer fabrication, as desired by operatingconditions such as part geometry.

In preferred embodiments, the intermediate is formed by continuousliquid interface production (CLIP). CLIP is known and described in, forexample, PCT Applications Nos. PCT/US2014/015486 (published as U.S. Pat.No. 9,211,678 on Dec. 15, 2015); PCT/US2014/015506 (also published asU.S. Pat. No. 9,205,601 on Dec. 8, 2015), PCT/US2014/015497 (alsopublished as US 2015/0097316, and to publish as U.S. Pat. No. 9,216,546on Dec. 22, 2015), and in J. Tumbleston, D. Shirvanyants, N. Ermoshkinet al., Continuous liquid interface production of 3D Objects, Science347, 1349-1352 (published online 16 Mar. 2015). In some embodiments,CLIP employs features of a bottom-up three dimensional fabrication asdescribed above, but the irradiating and/or said advancing steps arecarried out while also concurrently maintaining a stable or persistentliquid interface between the growing object and the build surface orwindow, such as by: (i) continuously maintaining a dead zone ofpolymerizable liquid in contact with said build surface, and (ii)continuously maintaining a gradient of polymerization zone (such as anactive surface) between the dead zone and the solid polymer and incontact with each thereof, the gradient of polymerization zonecomprising the first component in partially cured form. In someembodiments of CLIP, the optically transparent member comprises asemipermeable member (e.g., a fluoropolymer), and the continuouslymaintaining a dead zone is carried out by feeding an inhibitor ofpolymerization through the optically transparent member, therebycreating a gradient of inhibitor in the dead zone and optionally in atleast a portion of the gradient of polymerization zone.

In some embodiments, the stable liquid interface may be achieved byother techniques, such as by providing an immiscible liquid as the buildsurface between the polymerizable liquid and the optically transparentmember, by feeding a lubricant to the build surface (e.g., through anoptically transparent member which is semipermeable thereto, and/orserves as a reservoir thereof), etc.

While the dead zone and the gradient of polymerization zone do not havea strict boundary therebetween (in those locations where the two meet),the thickness of the gradient of polymerization zone is in someembodiments at least as great as the thickness of the dead zone. Thus,in some embodiments, the dead zone has a thickness of from 0.01, 0.1, 1,2, or 10 microns up to 100, 200 or 400 microns, or more, and/or thegradient of polymerization zone and the dead zone together have athickness of from 1 or 2 microns up to 400, 600, or 1000 microns, ormore. Thus the gradient of polymerization zone may be thick or thindepending on the particular process conditions at that time. Where thegradient of polymerization zone is thin, it may also be described as anactive surface on the bottom of the growing three-dimensional object,with which monomers can react and continue to form growing polymerchains therewith. In some embodiments, the gradient of polymerizationzone, or active surface, is maintained (while polymerizing stepscontinue) for a time of at least 5, 10, 15, 20 or 30 seconds, up to 5,10, 15 or 20 minutes or more, or until completion of thethree-dimensional product.

Inhibitors, or polymerization inhibitors, for use in the presentinvention may be in the form of a liquid or a gas. In some embodiments,gas inhibitors are preferred. In some embodiments, liquid inhibitorssuch as oils or lubricants may be employed. In further embodiments, gasinhibitors which are dissolved in liquids (e.g. oils or lubricants) maybe employed. For example, oxygen dissolved in a fluorinated fluid. Thespecific inhibitor will depend upon the monomer being polymerized andthe polymerization reaction. For free radical polymerization monomers,the inhibitor can conveniently be oxygen, which can be provided in theform of a gas such as air, a gas enriched in oxygen (optionally but insome embodiments preferably containing additional inert gases to reducecombustibility thereof), or in some embodiments pure oxygen gas. Inalternate embodiments, such as where the monomer is polymerized byphotoacid generator initiator, the inhibitor can be a base such asammonia, trace amines (e.g. methyl amine, ethyl amine, di and trialkylamines such as dimethyl amine, diethyl amine, trimethyl amine, triethylamine, etc.), or carbon dioxide, including mixtures or combinationsthereof.

The method may further comprise the step of disrupting the gradient ofpolymerization zone for a time sufficient to form a cleavage line in thethree-dimensional object (e.g., at a predetermined desired location forintentional cleavage, or at a location in the object where prevention ofcleavage or reduction of cleavage is non-critical), and then reinstatingthe gradient of polymerization zone (e.g. by pausing, and resuming, theadvancing step, increasing, then decreasing, the intensity ofirradiation, and combinations thereof).

CLIP may be carried out in different operating modes operating modes(that is, different manners of advancing the carrier and build surfaceaway from one another), including continuous, intermittent, reciprocal,and combinations thereof.

Thus in some embodiments, the advancing step is carried outcontinuously, at a uniform or variable rate, with either constant orintermittent illumination or exposure of the build area to the lightsource.

In other embodiments, the advancing step is carried out sequentially inuniform increments (e.g., of from 0.1 or 1 microns, up to 10 or 100microns, or more) for each step or increment. In some embodiments, theadvancing step is carried out sequentially in variable increments (e.g.,each increment ranging from 0.1 or 1 microns, up to 10 or 100 microns,or more) for each step or increment. The size of the increment, alongwith the rate of advancing, will depend in part upon factors such astemperature, pressure, structure of the article being produced (e.g.,size, density, complexity, configuration, etc.).

In some embodiments, the rate of advance (whether carried outsequentially or continuously) is from about 0.1.1, or 10 microns persecond, up to about to 100, 1,000, or 10,000 microns per second, againdepending again depending on factors such as temperature, pressure,structure of the article being produced, intensity of radiation, etc.

In still other embodiments, the carrier is vertically reciprocated withrespect to the build surface to enhance or speed the refilling of thebuild region with the polymerizable liquid. In some embodiments, thevertically reciprocating step, which comprises an upstroke and adownstroke, is carried out with the distance of travel of the upstrokebeing greater than the distance of travel of the downstroke, to therebyconcurrently carry out the advancing step (that is, driving the carrieraway from the build plate in the Z dimension) in part or in whole.

In some embodiments, the solidifiable or polymerizable liquid is changedat least once during the method with a subsequent solidifiable orpolymerizable liquid (e.g., by switching a “window” or “build surface”and associated reservoir of polymerizable liquid in the apparatus);optionally where the subsequent solidifiable or polymerizable liquid iscross-reactive with each previous solidifiable or polymerizable liquidduring the subsequent curing, to form an object having a plurality ofstructural segments covalently coupled to one another, each structuralsegment having different structural (e.g., tensile) properties (e.g., arigid funnel or liquid connector segment, covalently coupled to aflexible pipe or tube segment).

Once the three-dimensional intermediate is formed, it may be removedfrom the carrier, optionally washed, any supports optionally removed,any other modifications optionally made (cutting, welding, adhesivelybonding, joining, grinding, drilling, etc.), and then heated and/ormicrowave irradiated sufficiently to further cure the resin and form thethree dimensional object. Of course, additional modifications may alsobe made following the heating and/or microwave irradiating step.

Washing may be carried out with any suitable organic or aqueous washliquid, or combination thereof, including solutions, suspensions,emulsions, microemulsions, etc. Examples of suitable wash liquidsinclude, but are not limited to water, alcohols (e.g., methanol,ethanol, isopropanol, etc.), benzene, toluene, etc. Such wash solutionsmay optionally contain additional constituents such as surfactants, etc.A currently preferred wash liquid is a 50:50 (volume:volume) solution ofwater and isopropanol. Wash methods such as those described in U.S. Pat.No. 5,248,456 may be employed and are included therein.

After the intermediate is formed, optionally washed, etc., as describedabove, it is then heated and/or microwave irradiated to further cure thesame. Heating may be active heating (e.g., in an oven, such as anelectric, gas, or solar oven), or passive heating (e.g., at ambienttemperature). Active heating will generally be more rapid than passiveheating and in some embodiments is preferred, but passive heating—suchas simply maintaining the intermediate at ambient temperature for asufficient time to effect further cure—is in some embodiments preferred.

In some embodiments, the heating step is carried out at at least a first(oven) temperature and a second (oven) temperature, with the firsttemperature greater than ambient temperature, the second temperaturegreater than the first temperature, and the second temperature less than300° C. (e.g., with ramped or step-wise increases between ambienttemperature and the first temperature, and/or between the firsttemperature and the second temperature).

For example, the intermediate may be heated in a stepwise manner at afirst temperature of about 70° C. to about 150° C., and then at a secondtemperature of about 150° C. to 200 or 250° C., with the duration ofeach heating depending on the size, shape, and/or thickness of theintermediate. In another embodiment, the intermediate may be cured by aramped heating schedule, with the temperature ramped from ambienttemperature through a temperature of 70 to 150° C., and up to a final(oven) temperature of 250 or 300° C., at a change in heating rate of0.5° C. per minute, to 5° C. per minute. (See, e.g., U.S. Pat. No.4,785,075).

Microwave irradiation of the object for heating may be carried out atany suitable frequency, typically from 300 MHz to 300 GHz. In someembodiments, microwave irradiation of the object is carried out at afrequency of from 2,000 MHz to 4,000 MHz (2,450 MHz typically beingemployed in small or residential microwave ovens), or at a frequency offrom 500 MHz to 1,500 MHz (915 MHz typically being employed in largercommercial or industrial microwave ovens).

The heating step may be carried out by multiple heating methods as isknown in the art (e.g., a combination of two or more of radiant heating,microwave irradiating, convection heating, conduction heating, etc.)

In some embodiments, the heating step may be carried out in part or inwhole by generating sufficient heat during an initial forming byphotopolymerization step, where that photopolymerization step is anexothermic reaction.

It will be clear to those skilled in the art that the materialsdescribed in the current invention will be useful in other additivemanufacturing techniques, including ink-jet printer-based methods.

3. Products.

The resins and methods described herein are useful for, among otherthings, making three-dimensional objects that have high tensilestrength, high scratch resistance, high glass transition temperatures,good chemical resistance, and/or are good insulators. In someembodiments, the resins and methods described herein are used tofasteners; electronic device housings; gears, propellers, and impellers;wheels, mechanical device housings; tools, etc. “Fastener” includes, butis not limited to, nuts, bolts, screws, expansion fasteners, clips,buckles, etc. “Electronic device housing” includes, but is not limitedto, partial and complete cell phone housings, tablet computer housings,personal computer housings, electronic recorder and storage mediahousings, video monitor housings, keyboard housings, etc. “Mechanicaldevice housing” includes, but is not limited to, partial and completegear housings, pump housings, motor housings, etc.

In the Examples set forth below, the following reagents are used, exceptwhere indicated otherwise.

Epoxy: Araldite® GY 6010 bisphenol A epoxy liquid resin, available fromHuntsman Advanced Materials Americas, 10003 Woodloch Forest Drive, TheWoodlands, Tex. 77380 USA. This generally has the structure:

Hardener: Jeffamine D230, a polyetheramine characterized by repeatingoxypropylene units in the backbone, available from Huntsman Corp. 10003Woodloch Forest Drive, The Woodlands, Tex. 77380 USA. This generally hasthe structure:

Urethane Acrylate: Sartomer CN983 urethane acrylate, an aliphaticpolyester based urethane diacrylate oligomer available from SartomerAmericas, 502 Thomas Jones Way, Exton, Pa. 19341 USA.

Diluent: Sartomer SR231 diethylene glycol dimethacreylate, availablefrom Sartomer Americas, 502 Thomas Jones Way, Exton, Pa. 19341 USA. Thisgenerally has the structure:

Acrylated BPA epoxide: Sartomer CN153 epoxy acrylate oligomer, an epoxyacrylate oligomer that has both acrylate and epoxy functionality on thesame backbone, available from Sartomer Americas, 502 Thomas Jones Way,Exton, Pa. 19341 USA. This generally has the structure:

Photoinitiator: IRGACURE® TPO diphenyl(2,4,6,-trimethylbenzoyl)phosphineoxide photoinitiator, available from BASF Corporation, 100 Park Avenue,Florham Park, N.J. 07932 USA. This generally has the structure:

Example 1 Aromatic Amine Hardener Resin and Product

In this example, the hardener is 4,4′-Methylenebis(2,6-diethylaniline)(MDEA), an aromatic amine, which has the structure:

A resin composition containing the foregoing hardener was producedhaving the composition given in Table 1 below:

TABLE 1 Aromatic amine hardener resin. Component Name Approx % by weightEpoxy Huntsman Araldite GY 6010 30 Hardener MDEA 20 Urethane AcrylateSartomer CN983 25 Diluent Sartomer SR 231 (diethylene 18 glycoldimethacrylate) Acrylated BPA epoxy Sartomer CN153 6 PhotoinitiatorIrgacure ™ 369 1

Sartomer products are available from Sartomer Americas, 502 Thomas JonesWay, Exton, Pa. 19341 USA. Irgacure 369 is a product of Ciba SpecialtyChemicals. Huntsman products are available from Huntsman AdvancedMaterials Americas, 10003 Woodloch Forest Drive, The Woodlands, Tex.77380 USA.

A three-dimensional intermediate object was produced from the resin ofTable 1 by Continuous Liquid Interface Production (CLIP). In thisprocess, the shape of the intermediate object is determined or “lockedin” when the UV curable components react. Then, the epoxy and MDEAcomponents are believed to react in a second heating step inside thepart by the mechanism described in Scheme 1 below.

A typical heat curing schedule for an intermediate object produced withthe foregoing system is 2 hours at 180° C.

Example 2 Polyether Amine Hardener Resin and Product

In this example the hardener is a polyether amine, specificallyJeffamine D230™ (available from Huntsman Petrochemical Co.), thestructure of which is given above. A resin system containing thishardener was produced with the composition given in Table 2 below.

TABLE 2 Polyether amine hardener resin. Component Name % by weight EpoxyHuntsman Araldite GY 6010 12.5 Hardener Jeffamine D230 7 UrethaneAcrylate Sartomer CN983 40 Diluent Sartomer SR 231 30 Acrylated BPAepoxy Sartomer CN153 10 Photoinitiator TPO 0.5Three-dimensional intermediate objects were produced from the resinsystem of Table 2 by CLIP, with the shape of the object being “lockedin” by UV light as described in Example 1. The epoxy and Jeffamine D230react in a second heating cure step by the same mechanism in Example 1.An example cure schedule for this system is 80° C. for 2 hours followedby 125° C. for 3 hours.

Example 3 Anhydride Hardener Resin and Product

In this example, the hardener is an anhydride with an acceleratorpresent to speed the cure. Structures of the anhydride (methyltetrahydrophthalic anhydride, MTHPA) and the accelerator(benzyldimethylamine, BDMA) are shown below.

A resin system containing this hardener and accelerator was producedhaving the composition given in Table 3 below.

Three dimensional intermediate objects were produced from the resin ofTable 3 by CLIP, essentially as described in Examples 1-2 above. In thisexample, the epoxy and anhydride are believed to react at hightemperature in a mechanism detailed by DOW chemical as shown in Scheme 2below.

TABLE 3 Anhydride hardener resin. Component Name Approx. % by weightEpoxy Huntsman Araldite GY 6010 10 Hardener MTHPA 9 Accelerator BDMA 0.5Urethane Acrylate Sartomer CN983 40 Diluent Sartomer SR 231 30 AcrylatedBPA epoxy Sartomer CN153 10 Photoinitiator TPO 0.5

An example cure schedule for this system is 90° C. for 2 hours followedby 150° C. for 4 hours.

Examples 4-6 Improved Products from Resins Further Containing anAcrylated Epoxy

Addition of the acrylated epoxy CN153 (available from Sartomer Americas)to each of the resin compositions given in Examples 1-3 above chemicallyconnects the UV and epoxy networks through it's dual functionalityduring production of the three-dimensional object by CLIP. Compared toidentical formulations without the component, addition of CN153 to theresins described above (at about three percent by weight in each of theformulations described above), reduces cracking with the aromatic amineand anhydride hardener systems, and reduces phase separation (asevidenced by opacity during printing) with the polyether amine hardenersystem, as shown in FIGS. 1-3.

Example 7 Resin Viscosity and Product Properties

Resins as described herein above typically have a viscosity of from 100or 200 to 10,000 or 20,000 Centipoise, or more, at room temperature(e.g., 25° C.).

Three-dimensional objects produced by CLIP from resins such as thosedescribed herein above typically have properties as given in Table 4below.

TABLE 4 Product properties. Tensile Strength 50 or 70 MPa to 100 or 200MPa Modulus 2,000 or 3,000 MPa to 5,000 or 7,000 MPa Elongation 5 to 10%Impact Strength 40 or 50 to 70 or 100 J/m Glass transition temperature50 or 60 to 100 or 120° C.

Example 8 Tough Epoxy Formulation Using a Core-Shell Rubber Filler

This resin formulation was made to produce products having higherelongation while maintaining a relatively high modulus by adding acore-shell rubber (CSR) modifier and switching the diluent to the moreflexible poly(ethylene glycol) dimethacrylate. The modifier is availablefrom Kaneka pre-dispersed in DGEBA epoxy resin.

TABLE 5 Resin formulation. Component Name % by weight CSR-modified MX17012.5 Epoxy Hardener Jeffamine D230 7 Urethane Acrylate Sartomer CN983 40Diluent Sartomer SR 210 30 Acrylated BPA Sartomer CN153 10 epoxyPhotoinitiator TPO 0.5Typical properties of products with the resin by bottom up threedimensional fabrication (particularly CLIP) followed by a heat cure asdescribed above are as follows:

TABLE 6 Resin and Product properties. Resin viscosity 750 cP TensileStrength 50-60 MPa Modulus 2500-3500 MPa Elongation 20-40% ImpactStrength 40-60 J/m Glass transition 60-80° C. temp

Example 9 High Temperature Epoxy Formulation Including a Latent Hardener

In this example the hardener is an aromatic amine, diaminodiphenylsulfone (DDS). DDS is commonly used to cure epoxy and achievehigh Tg materials in other applications. The DDS used is amicropulverized solid and dispersed in the resin. The cure schedule is aramped cure schedule as described previously.

TABLE 7 Resin formulation. Component Name % by weight Epoxy MX153 46.5Hardener Aradur 9664-1 9.5 Urethane Acrylate Sartomer CN983 18.5 DiluentSartomer SR 248 24 Photoinitiator TPO 1.5Typical properties of products produced with the resin by bottom upthree dimensional fabrication (particularly CLIP) followed by a heatcure as described above are as follows:

TABLE 8 Resin and Product properties. Resin viscosity 6000 cP Tensile60-80 MPa Strength Modulus 3000-4500 MPa Elongation 3-8% Impact TBDStrength Glass transition 150-190° C. temp

The foregoing is illustrative of the present invention, and is not to beconstrued as limiting thereof. The invention is defined by the followingclaims, with equivalents of the claims to be included therein.

We claim:
 1. A method of forming a three-dimensional object, comprising:(a) providing an epoxy dual cure resin; (b) forming a three-dimensionalintermediate from said resin, where said intermediate has the shape of,or a shape to be imparted to, said three-dimensional object, and wheresaid resin is solidified by exposure to light; then (c) optionallywashing the three-dimensional intermediate, and (d) heating and/ormicrowave irradiating said three-dimensional intermediate sufficientlyto further cure said resin and form said three-dimensional object;wherein said epoxy dual cure resin comprises: (i) a photoinitiator; (ii)monomers and/or prepolymers that are polymerizable by exposure toactinic radiation or light; (iii) optionally, a light absorbing pigmentor dye; (iv) an epoxy resin; (v) optionally, but in some embodimentspreferably, an organic hardener co-polymerizable with said epoxy resin;(vi) optionally but preferably a dual reactive compound havingsubstituted thereon a first reactive group reactive with said monomersand/or prepolymers that are polymerizable by exposure to actinicradiation or light, and a second reactive group reactive with said epoxyresin (e.g., an epoxy acrylate); (vii) optionally a diluent; (viii)optionally a filler; and (ix) optionally, a co-monomer and/or aco-prepolymer.
 2. The method of claim 1, wherein said epoxy resincomprises a bisphenol A epoxy resin, a bisphenol F epoxy resin, anovolac epoxy resin, an aliphatic epoxy resin, a glycidylamine epoxyresin, an epoxidized vegetable oil, or a combination thereof.
 3. Themethod of claim 1, wherein: said hardener comprises an amine (e.g., anaromatic amine, a cycloaliphatic amine, an aliphatic amine such as apolyether amine, etc.); and/or said epoxy resin comprises a catalyzedepoxy resin.
 4. The method of claim 1, wherein said hardener comprisesan acid, a phenol, an alcohol, a thiol, or an anhydride.
 5. The methodof claim 1, wherein said hardener comprises a latent hardener,optionally included in said polymerizable liquid in solid particulateform (e.g., as a micronized solid).
 6. The method of claim 1, saidmonomers and/or prepolymers polymerizable by exposure to actinicradiation or light comprising reactive end groups selected from thegroup consisting of acrylates, methacrylates, α-olefins, N-vinyls,acrylamides, methacrylamides, styrenics, epoxides, thiols, 1,3-dienes,vinyl halides, acrylonitriles, vinyl esters, maleimides, and vinylethers.
 7. The method of claim 1, wherein said light absorbing pigmentor dye is: (i) titanium dioxide (e.g., in an amount of from 0.05 or 0.1to 1 or 5 percent by weight), (ii) carbon black (e.g., in an amount offrom 0.05 or 0.1 to 1 or 5 percent by weight), and/or (iii) an organicultraviolet light absorber (e.g., a hydroxybenzophenone,hydroxyphenylbenzotriazole, oxanilide, benzophenone, thioxanthone,hydroxyphenyltriazine, and/or benzotriazole ultraviolet light absorber)(e.g., in an amount of 0.001 or 0.005 to 1 or 2 percent by weight). 8.The method of claim 1, wherein said diluent comprises an acrylate, amethacrylate, a styrene, an acrylic acid, a vinylamide, a vinyl ether, avinyl ester, polymers containing any one or more of the foregoing, andcombinations of two or more of the foregoing.
 9. The method of claim 1,wherein said filler is present and comprises a core-shell rubber. 10.The method of claim 1, wherein said resin comprises: (i) from 0.1 to 4percent by weight of said photoinitiator, (ii) from 10 to 90 percent byweight of said monomers and/or prepolymers that are polymerizable byexposure to actinic radiation or light, (iii) from 0.1 to 2 percent byweight of said light absorbing pigment or dye when present, (iv) from 2,5 or 10 to 50 or 60 percent by weight of said epoxy resin; (v) from 1 or2 to 30 or 40 percent by weight of said organic hardener when present;(vi) from 1 or 2 to 30 or 40 percent by weight of said dual reactivecompound when present; (vii) from 1 to 40 percent by weight of saiddiluent when present; and (viii) from 1 to 50 percent by weight of saidfiller when present.
 11. The method of claim 1, wherein said formingstep is carried out by additive manufacturing (e.g., bottom-up ortop-down three-dimensional fabrication).
 12. The method of claim 1,wherein said forming step is carried out by: (i) by either bottom-upthree dimensional fabrication between a carrier and a build surface ortop-down three dimensional fabrication between a carrier and a filllevel, the fill level optionally defined by a build surface; and/or(ii), optionally with a stationary build surface; and/or (iii)optionally while maintaining the resin in liquid contact with both theintermediate object and the build surface, and/or (iv) optionally withsaid forming step carried out in a layerless manner, each during theformation of at least a portion of the three dimensional intermediate.13. The method of claim 1, wherein said forming step is carried out bycontinuous liquid interface production (CLIP).
 14. The method of claim13, wherein said forming step is carried out between a carrier and abuild surface, said method further comprising vertically reciprocatingsaid carrier with respect to the build surface to enhance or speed therefilling of the build region with the polymerizable liquid.
 15. Themethod of claim 1, wherein said three-dimensional object comprises apolymer blend, interpenetrating polymer network, semi-interpenetratingpolymer network, or sequential interpenetrating polymer network.
 16. Themethod of claim 1, wherein said heating step is carried out at at leasta first temperature and a second temperature, with said firsttemperature greater than ambient temperature, said second temperaturegreater than said first temperature, and said second temperature lessthan 300° C. (e.g., with ramped or step-wise increases between ambienttemperature and said first temperature, and/or between said firsttemperature and said second temperature).
 17. An epoxy dual cure resinuseful for additive manufacturing of three-dimensional objects,comprising: (i) a photoinitiator; (ii) monomers and/or prepolymers thatare polymerizable by exposure to actinic radiation or light; (iii)optionally, a light absorbing pigment or dye; (iv) an epoxy resin; (v)optionally, but in some embodiments preferably, an organic hardenerco-polymerizable with said epoxy resin; (vi) optionally but preferably adual reactive compound having substituted thereon a first reactive groupreactive with said monomers and/or prepolymers that are polymerizable byexposure to actinic radiation or light, and a second reactive groupreactive with said epoxy resin (e.g., an epoxy acrylate); (vii)optionally a diluent; (viii) optionally a filler; and (ix) optionally, aco-monomer and/or a co-prepolymer.
 18. The resin of claim 17, whereinsaid epoxy resin comprises a bisphenol A epoxy resin, a bisphenol Fepoxy resin, a novolac epoxy resin, an aliphatic epoxy resin, aglycidylamine epoxy resin, an epoxidized vegetable oil, or a combinationthereof.
 19. The resin of claim 17, wherein: said hardener is presentand comprises an amine (e.g., an aromatic amine, a cycloaliphatic amine,an aliphatic amine such as a polyether amine, etc.); and/or said epoxyresin comprises a catalyzed epoxy resin.
 20. The resin of claim 17,wherein said hardener is present and comprises an acid, a phenol, analcohol, a thiol, or an anhydride.
 21. The resin of claim 17, whereinsaid hardener is present and comprises a latent hardener.
 22. The resinof claim 17, said monomers and/or prepolymers polymerizable by exposureto actinic radiation or light comprising reactive end groups selectedfrom the group consisting of acrylates, methacrylates, α-olefins,N-vinyls, acrylamides, methacrylamides, styrenics, epoxides, thiols,1,3-dienes, vinyl halides, acrylonitriles, vinyl esters, maleimides, andvinyl ethers.
 23. The resin of claim 17, wherein said light absorbingpigment or dye is: (i) titanium dioxide (e.g., in an amount of from 0.05or 0.1 to 1 or 5 percent by weight), (ii) carbon black (e.g., in anamount of from 0.05 or 0.1 to 1 or 5 percent by weight), and/or (iii) anorganic ultraviolet light absorber (e.g., a hydroxybenzophenone,hydroxyphenylbenzotriazole, oxanilide, benzophenone, thioxanthone,hydroxyphenyltriazine, and/or benzotriazole ultraviolet light absorber)(e.g., in an amount of 0.001 or 0.005 to 1 or 2 percent by weight). 24.The resin of claim 17, wherein said diluent comprises an acrylate, amethacrylate, a styrene, an acrylic acid, a vinylamide, a vinyl ether, avinyl ester, polymers containing any one or more of the foregoing, andcombinations of two or more of the foregoing.
 25. The resin of claim 17,wherein said filler is present and comprises a core-shell rubber. 26.The resin of claim 17, wherein said polymerizable liquid comprises: (i)from 0.1 to 4 percent by weight of said photoinitiator, (ii) from 10 to90 percent by weight of said monomers and/or prepolymers that arepolymerizable by exposure to actinic radiation or light, (iii) from 0.1to 2 percent by weight of said light absorbing pigment or dye whenpresent, (iv) from 2, 5 or 10 to 50 or 60 percent by weight of saidepoxy resin; (v) from 1 or 2 to 30 or 40 percent by weight of saidorganic hardener when present; (vi) from 1 or 2 to 30 or 40 percent byweight of said dual reactive compound when present; (vii) from 1 to 40percent by weight of said diluent when present; and (viii) from 1 to 50percent by weight of said filler when present.
 27. A product produced bya method of claim
 1. 28. An intermediate product produced by a method ofclaim 1 before carrying out said heating and/or microwave irradiatingstep (c).
 29. The method of claim 1, wherein said dual reactive compoundcomprises a compound of the formula: (X)_(n)R(X′)_(m), wherein: X is thefirst reactive group selected from the group consisting of acrylate,methacrylate, α-olefin, N-vinyl, acrylamides, methacrylamide, styrenic,thiol, 1,3-diene, vinyl halide, acrylonitrile, vinyl ester, maleimide,and vinyl ether reactive groups, and combinations thereof; X′ is thesecond reactive group selected from the group consisting of epoxy,amine, isocyanate, alcohol, and anhydride reactive groups, andcombinations thereof n and m are each integers of from 1 or 2 to 10 or20, and R is a hydrocarbyl group.